26
GAS SUPPLY (cont.)
GAS PRESSURE
SETTING GAS PRESSURE
The maximum gas supply pressure to the furnace must not
exceed 10.5" w.c. natural gas, or 13" w.c. LP gas.
The mini-
mum supply gas pressure to the gas valve should be 5
⬙
w.c. nat-
ural gas or 11
⬙
w.c. LP gas. A properly calibrated manometer is
required for accurate gas pressure measurements.
SUPPLY GAS PRESSURE
MEASUREMENT
An inlet pressure tap is on the input side of the gas valve.
1. With gas shut off to the furnace at the manual gas valve out-
side the unit, remove the inlet pressure tap plug.
2. Connect a manometer to the pressure tap.
3. Turn on the gas supply and operate the furnace and all other
gas-fired units on the same gas line as the furnace.
4. Note or adjust the line gas pressure to give:
A. 5
⬙
- 10.5
⬙
w.c. for natural gas.
B. 11
⬙
- 13
⬙
w.c. for LP gas.
5. Shut off the gas at the manual gas valve and remove the
manometer and hose.
6. Replace the pressure tap plug before turning on the gas.
7. Turn on the gas supply and check for gas leaks using an ap-
proved leak detector. Do NOT use a flame of any kind to
check for leaks. Repair any leaks and repeat.
If the supply gas line pressure is above these ranges,a high pres-
sure in line gas regulator may be required. Consult local gas util-
ity. With LP gas, have the LP supplier reduce the line pressure at
the regulator.
If supply gas line pressure is below these ranges, either remove
any restrictions in the gas supply piping or enlarge the gas pipe.
See Tables 7 and 8. With LP gas, have the LP supplier adjust the
line pressure at the regulator.
Manifold Gas Pressure Measurement. Natural gas manifold
pressure should be 3.5" w.c. LP gas manifold pressure
should be 10.0" w.c.
Only small variations in gas pressure
should be made by adjusting the pressure regulator.
1. With the gas to the unit shut off at the manual gas valve, re-
move the outlet pressure tap plug.
2. Connect a manometer to this pressure tap.
3. Turn on the gas supply and operate the furnace (apply a
heat call).
4. Note or adjust the manifold gas pressure to give:
A. 3.5
⬙
w.c. for natural gas.
B. 10.0
⬙
w.c. for LP gas.
5. To adjust the pressure regulator, remove the regulator cap.
(See Figure 20.)
6. Turn the adjustment screw clockwise to increase pressure,
or counterclockwise to decrease pressure.
7. Securely replace the regulator cap.
8. Shut off gas at the manual gas valve and remove the
manometer and hose.
9. Replace the pressure tap plug before turning on the gas.
10. Turn on the gas supply and apply a heat call to the furnace
then check for gas leaks using an approved leak detector.
Do NOT use a flame of any kind to check for leaks. Repair
any leaks and repeat.
Ga
s S
up
pl
y
!
CAUTION
ELEVATIONS ABOVE 2000 FT. REQUIRE THAT THE FUR-
NACE INPUT RATING BE ADJUSTED AND THAT THE SIZE
OF THE BURNER ORIFICES BE RECALCULATED BASED
ON ELEVATION AND GAS HEATING VALUE. THE BURNER
ORIFICES MAY (OR MAY NOT) NEED TO BE CHANGED.
SEE THE SECTION TITLED “HIGH ALTITUDE INSTALLA-
TIONS” OF THIS BOOK FOR INSTRUCTIONS.
Summary of Contents for 801P SERIES
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